Rotary kilns, or calciners, are used to cause thermal decomposition, phase transition, or removal of volatile fractions from ores and other solid materials in the presence of air. The most familiar calcine (a word that refers to any product produced by the process) is Portland cement, which is produced from limestone (calcium carbonate) as the decomposition product calcium oxide.
Typically, temperature vs. time should be carefully controlled in rotary kilns to provide sufficient energy without exceeding a melting point of the product. Lime kilns (as Portland cement-producing rotary kilns may be commonly referred to) tend to be somewhat tricky to operate for producing optimum product. Temperatures that are too high or too low, or treatment times that are too long or too short can result in sub-par product that does not yield favorable market demand or price. Operation of rotary kilns may be complicated by variations in co-fired fuels (such as tires) that are introduced into the kilns along with raw materials for producing the product.
What is needed is a technology that can maintain consistent desirable kiln conditions and/or adapt to changing operating conditions, while minimizing undesirable flue gases such as oxides of nitrogen (NOx) and carbon monoxide (CO).